According to the New York Times, Shirley Sotloff addresses Mr. Baghdadi as caliph and calls on him to exercise his right to show clemency, as other previous caliphs have, stretching back to the immediate successors of the Prophet Muhammad.

In an emotional video she says:

As a mother, I ask your justice to be merciful and not punish my son for matters he has no control over.
I ask you to use your authority to spare his life and to follow the example set by the Prophet Muhammad, who protected the People of the Book.